A 41-year-old woman arrived in a Hawaii emergency department with her husband early in the morning. The nursing triage note indicated vomiting with dizziness and tingling in her hands.

History revealed the patient and four family members had eaten fish for dinner, an 18-inch grouper. Her husband reported she had had similar symptoms about five years prior to this situation, also after eating fish. The patient was the only family member to eat the head of the fish. The island of Oahu had experienced extremely heavy rainstorms the week prior.

Initial vital signs were: temperature of 36.8 degrees Celsius (98.2 degrees Fahrenheit), pulse of 57, respiratory rate of 18, blood pressure of 106 over 57. Physical examination was remarkable for a tired and uncomfortable appearing woman. Sensation in the hands was intact, with no discernible abnormalities related to touching a cold surface. An EKG was performed on arrival, showing no abnormalities. The patient was treated with droperidol for nausea, which cured the vomiting. One hour later, heart rate decreased to 42 and the blood pressure dropped to 80 over 45. One liter of saline was given. Labs were unremarkable. Blood pressure improved with the saline bolus. The patient felt better and was discharged at 7:30 a.m. with instructions related to avoiding future exposure.

Ciguatera fish poisoning, a foodborne illness caused by consuming reef fish contaminated with ciguatoxins, is characterized by a combination of gastrointestinal, neurological, and cardiovascular symptoms. It is more common in tropical areas. The World Health Organization estimates that between 50,000 and 500,000 people are affected by ciguatoxin yearly, indicating that reporting is limited.¹ Ciguatoxins are difficult to detect and quantify: They are odorless, tasteless, heat stable, and present at very low levels in contaminated seafood.¹ Friedman and colleagues indicate regional levels of risk.³ If water temperatures continue to rise, the distribution of ciguatera poisoning may change.

The triage note for this patient offered a clue to the cause of the vomiting: altered sensation in the hands. Cold allodynia—the sensation that cold things feel hot to the touch is nearly pathognomonic for ciguatera poisoning.¹ The patient indicated that washing her hands in cold water felt strange.

Grouper are among the species of fish commonly associated with ciguatera. The local marine ecosystem, especially after heavy rains, can foster the growth of the microalgae that produce ciguatoxins. These toxins are then bioaccumulated up the food chain, from smaller fish to larger predatory reef fish like groupers. The most common species implicated in ciguatera poisoning include barracuda, grouper, snapper, wrasse, moray eel, and parrotfish.² The toxicity of fish can be dependent on the species, size, seasonal variations, water temperature, and location.

The consumption of certain parts of the fish, such as the head, guts, liver, or roe, poses a higher risk for ciguatera poisoning because these parts can contain higher concentrations of the toxin.² Cooking, drying, salting, and freezing do not destroy ciguatoxins.¹ The California Department of Public Health recommends that patients recovering from ciguatera should avoid eating reef fish, fish sauces, shellfish, nuts/nut oils, and alcoholic beverages for up to six months, because these foods may provoke a recurrence. Future exposure can result in more severe symptoms.⁴

Treatment of ciguatera poisoning is supportive and symptomatic. Mannitol has been used; the literature is mixed related to potential benefit. Hospitalization may be necessary for persistent symptoms.

Take-home points include the following:

• Ciguatera poisoning can cause gastrointestinal, cardiac, and neurologic symptoms.
• An altered reaction to cold can be considered confirmatory.
• Periods of heavy rain increase the risk of ciguatera poisoning.
• Reef fish are most often implicated.
• The head, liver, and roe are riskier parts of the fish to eat than the flesh.
• Prior exposure increases the risk of symptoms from repeat exposure.
• Treatment is symptomatic.
• Hospitalization may be necessary for persistent symptoms.
• Patients should be warned about potential future recurrent symptoms.

In conclusion, avoid eating reef fish after periods of heavy rain, especially the head or roe.

Dr. Baker, a Hawaii-based emergency physician with a long-standing interest in toxicology, finds himself both fascinated and concerned by the dangers posed by natural toxins like ciguatera and manmade ones like methamphetamine.

References

1. WHO Department of Food Safety and Zoonoses. Ciguatera poisoning. World Health Organization. Published November 2020. Accessed July 15, 2024.
2. National Center for Emerging and Zoonotic Infectious Diseases. Food poisoning from seafood. Centers for Disease Control and Prevention. Updated March 30, 2022. Accessed July 15, 2024.
3. Friedman MA, Fleming LE, Fernandez M, et al. Ciguatera fish Poisoning: treatment, prevention and management. Mar Drugs. 2008;6(3):456-479.
4. State of California Health and Human Services Agency. Ciguatera fish poisoning fact sheet. California Department of Public Health Division of Communicable Disease. Published December 2017. Accessed July 15, 2024.